Bertrand Bonello's Saint Laurent is a celebratory and swooningly submissive tribute to the fashion designer Yves Saint Laurent. It is hugely narcissistic, colossally long - and for all its apparently feminised sensibility and solemn talk of Saint Laurent's pioneering sympathy with women, it is as macho and phallus-worshipping as any Schwarzenegger action movie. This butterfly doesn't get broken on any wheel - it smashes the wheel to pieces.

It is in fact arguably superior to a recent, similar movie on the same subject - Jalil Lespert's Yves Saint Laurent - which contrived to look like a YSL corporate in-house video. This film is handsomely designed and photographed and does take a keener look at Saint Laurent's desperate loneliness and his shallow, jaded pleasures, although it is no less forgiving, no less respectful, no less convinced of Saint Laurent's importance as a popular artist, and really no better at persuading the non-fashionista laity, which I confess includes me.

Saint Laurent is played by Gaspard Ulliel: far more thrustingly sexy than Pierre Niney's boy aesthete in the previous movie. Jeremie Renier is his lover and business partner, Pierre Bergé, the man who cosseted and protected the creative man himself while shrewdly building the corporate brand. He forgave his lover's adventures with drugs and boys, perhaps because Bergé suspected that these fleeting moments of sensuality were somehow connected to Saint Laurent's inspiration at the drawing board and his mastery of fashion's ephemeral art.

This skittering, hectic world is interrupted by immense stretches of exquisite ennui - languor and longueur combined. Saint Laurent is surrounded by an entourage of hangers-on, lovers and admirers, all of whom appear to have the same cynical smirk. They are often to be seen draped around couches, rugs, nightclub banquettes - smoking and smirking, drenched in sophisticated decadence and self-congratulation. Sometimes they and Saint Laurent himself are shown waking from the previous night's debauch, and their bleary demeanour doesn't change much. Almost everyone has a lit cigarette in the mouth - perfectly plausible for the 60s and 70s. One assistant, Loulou (Lea Seydoux) even fixes a model's collar with a cigarette on the go, surely putting her at risk of getting fag-ash down the back of the neck.

In the atelier itself, during the day, Saint Laurent is coolly authoritative. He inspects a model's outfit and muses: "We could raise the crotch to avoid whiskering. Or we could play on the whiskering." His staff are serious, soberly professional, dressed in white jackets like dentists or lab assistants - and not outrageously obnoxious like Saint Laurent's associates of the night, who are given to pouring out champagne pyramid-towers, like George Best. But are the jet-setting party animals supposed to be obnoxious? We are invited to compare them to the figures that populated Proust's belle époque. Well - maybe. Visconti had his Damned. Perhaps these people are supposed to be the Blessed. The point could be to show what it all cost Saint Laurent - and yet it doesn't actually seem to have cost him that much: he grows to a pampered old age, not very conspicuously interested in anyone or anything but his dog. Perhaps it is that they are entirely without affect, like a tableau by Warhol, who writes Saint Laurent a fan letter here.

Finally, Saint Laurent is a well made but bafflingly airless and claustrophobic film, like being with fashion's very own Tutenkhamen , living and dying inside his own richly appointed tomb - and sentimentally indulged to the last.